<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Rain Animation</title>
</head>
<body>
  <div class="container">
    <div class="cloud"></div>
  </div>
  <style>
    * {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 100vh;
  background-color: #1b1b1b;
}

.container {
  position: relative;
  width: 100%;
  height: 400px;
  display: flex;
  justify-content: center;
  border-bottom: 1px solid rgba(255, 255, 255, .1);
}

.container .cloud {
  position: relative;
  width: 320px;
  height: 100px;
  background-color: #fff;
  border-radius: 100px;
  filter: drop-shadow(8px 8px 0 #0005);
  animation: animateCloud 2s steps(1) infinite;
}

@keyframes animateCloud {
  0% {
    filter: drop-shadow(8px 8px 0 #0001) drop-shadow(0 0 0 #fff) brightness(1);
  }
  95% {
    filter: drop-shadow(8px 8px 0 #0001) drop-shadow(0 0 50px #fff5)  brightness(10);
  }

}

.container .cloud::before {
  content: '';
  position: absolute;
  top: -50px;
  left: 40px;
  width: 110px;
  height: 110px;
  border-radius: 50%;
  background-color: #484f59;
  box-shadow: 90px -10px 0 30px #484f59;
}

.container .cloud::after {
  content: '';
  position: absolute;
  inset: 0;
  background-color: #484f59;
  border-radius: 100px;
  z-index: 1000;
}

.container .cloud .drop {
  position: absolute;
  top: 40px;
  background-color: #05a2eb;
  width: 2px;
  height: 10px;
  transform-origin: bottom;
  animation: animate 2s linear infinite;
}

@keyframes animate {
  0% {
    transform: translateY(0) scaleY(1);
  }
  70% {
    transform: translateY(360px) scaleY(1);
  }
  80% {
    transform: translateY(360px) scaleY(.2);
  }
  100% {
    transform: translateY(360px) scaleY(0) scaleX(15);
  }
}
  </style>
  <script>
    function rain() {
      const cloud = document.querySelector('.cloud'),
            e = document.createElement('div'),
            left = Math.floor(Math.random() * 310),
            width =  Math.random() * 5,
            height = Math.random() * 50,
            duration = Math.random() * 0.5

      e.classList.add('drop')
      cloud.appendChild(e)  
      e.style.left = left + 'px'
      e.style.width =0.5 + width + 'px'
      e.style.height =0.5 + height + 'px'
      e.style.animationDuration = 1 + duration + 's'
      setTimeout(() => {
        cloud.removeChild(e)
      },2000)
    }

    setInterval(() => {
      rain()
    },20)
  </script>
</body>
</html>